Method for operating hot blast stove

ABSTRACT

A method for operating a hot blast stove characterized in that when intermittently operating a plurality of hot blast stoves each having a pressure supply valve, a cold blast valve, a stack valve, a hot blast valve and the like, the blast pressure within the hot blast stove at the time of transfer to the regeneration process after completion of the blast process is supplied by means of the pressure supply valves to another hot blast stove in which the &#39;&#39;&#39;&#39;on blast&#39;&#39;&#39;&#39; state is going to start after completion of regeneration, thereby effectively utilizing the residual pressure and heat.

United States Patent Ono et al. Oct. 14, 1975 [54] METHOD FOR OPERATING HOT BLAST [56] References Cited STOVE UNITED STATES PATENTS [75] Inventors: Yoshio Ono, Kure; Minoru Kosugi, 1,880,229 10/1932 Andrews et a1 432/30 Kita-Kyushu; Okihiko Kan, Kawasaki; Mitsuru Ohde, Hirakata, Primary Examiner-John J. Camby all of Japan Attorney, Agent, or Firm-Wenderoth, Lind & Ponack [73] Assignees: Nisshin Seiko Kabushiki Kaisha;

Shin-Nippon Seitetsu Kabushiki [57] ABSTRACT K i h F ji D ki s i K b hiki A method for operating a hot blast stove characterized Kai h K ki; K b t T kk in that when intermittently operating a plurality of hot Kabu hiki Kai ha, O k ll f blast stoves each having a pressure supply valve, a Japan cold blast valve, a stack valve, a hot blast valve and the like, the blast pressure within the hot blast stove at [22] Flled June 1974 the time of transfer to the regeneration process after [21] A L NO,1 477,161 completion of the blast process is supplied by means of the pressure supply valves to another hot blast stove in which the on blast state is going to start after [52] US. Cl. 432/30; 432/219, 432/221 Completion of regeneration thereby effectively min} [5 Int. Cl.2 the residual pressure d ea [58] Field of Search 4.32/29, 30, 219, 221

1 Claim, 3 Drawing Figures SVBa CV3 SVAz l AVa Sheet 1 of 3 U.S. Patent Oct. 14, 1975 US. Patent Oct. 14, 1975 Sheet 2 of 3 3,912,444

US. Patent Oct. 14, 1975 Sheet 3 of 3 METHOD FOR OPERATING HOT BLAST STOVE The present invention relates to a method for operating a hot blast stove and in particular a method for intermittently operating a plural number of hot blast stoves.

The operation of a hot blast stove in case intermittent operation will be described hereinunder.

For generating hot air to supply to a blast furnace, a plural number of stoves are provided for each blast furnace. Each hot blast stove comprises a combustion chamber and a regeneration chamber, regenerative bricks being heated during the combustion process, cooling air being passed through the regenerative bricks during the blast process, whereby air heated by the regenerative bricks is supplied to the blast furnace.

According to a conventional method, either a small port of a cold blast valve, the first valve in the-blasting system, or a pressure supply valve is opened in order to start the blast process after completion of the combustion process. A problem arising in this instance is the decline of blast pressure. That is, pressure control of the blower for supplying blast to the blast furnace and adjustment of the opening of the small port and the pressure supply valve is necessitated so as to prevent fall of pressure in the main blast pipe and the hot air supply pipe, respectively. However, the variation of the blast pressure and that of the amount of blast flow complicated curves not conforming to the predetermined conditions. Moreover, the switchover requires a considerably long period of time resulting in disadvantageous loss of efficiency in the operation of the blast furnace.

An objective of the present invention is to eliminate the aforementioned defects involved in the conventional method.

This and other objects are accomplished by the parts, improvement, combinations and arrangements comprising the present invention, a preferred embodiment of which is shown by way of examples in the annexed drawings and herein described in detail. Various modifications or changes in details of construction are comprehended within the scope of the appended claim.

FIG. 1 shows a schematic layout of four hot blast stoves for embodying the method of this invention.

FIG. 2 is a schedule showing the state of operation of each part of the foregoing.

FIG. 3 I is a diagram of a schedule showing the relation between the blast and combustion in each stove.

FIG. 3 II is a diagram showing the variation of pressure in each stove.

In FIGS. 1, lHS, ZHS, 3H8 and 4HS designate hot blast stoves respectively, a regeneration chamber 12 and a combustion chamber 13 being provided in each said stove. Numeral l1 designates a main blast pipe, 11 communicating with each regeneration chamber 12 of respective hot blast stove lHS 4I-IS through each cold blast valves CV CV A cold blast branch pipe 18 is connected to an intermediate portion of a pipe connecting each regenerating chamber 12 of each blast stove lHS 4HS to each cold blast valve CV, CV through respective pressure supply values PSV PSV a primary pressure supply valve PSV common to each stove being provided adjacent to the connection of the cooling air branch pipe 18 to the main pipe 11.

Numeral l4 designates a flue connected to a stack 19. The flue l4 communicates with each regeneration chamber 12 of each of hot blast stove lHS 4H8 through stack valves SVA SVA SVA SVA and SVB SVB SVB SVB respectively. Numeral 15 designates a hot blast main pipe, the hot blast main pipe 15 communicating with each combustion chamber 13 of respective hot blast stove lHS 4H8 through each hot blast valves HV I-IV Numeral l6 designates a combustion air pipe connected to each combustion chamber 13 of each hot blast stove 1I-IS 4I-IS. Intermediately on each said pipe 16 is mounted an air shut off valve AV to AV respectively. Numeral 17 designates a gas pipe and in each said gas pipe 17 is mounted a gas shut-off valve BV BV, and a primary gas valve GV GV respectively.

Referring now to FIG. 1, the first hot blast stove 11-18 is in the state of on gas when the stack valves SVA,, SVB, are opened and the air shut-off valve AV the primary gas valve GV and the gas shut-off valve BV are opened. In this case, combustion gas enters through the gas pipe 17, said combustion gas being mixed with air supplied through the air pipe 16 and burned within the combustion chamber 13 of hot blast stove lI-IS, said combustion gas after heating the regenerative bricks within the regeneration chamber 12 by changing its course in the upper part of the combustion chamber 13 being discharged into the stack 19 through the flue 14. Next, the hot blast stove lI-IS is in the state of on blast when the cold blast valve CV and the hot blast valve I-IV are opened. Originally, when a single unit is on blast, the primary pressure supply valve PSV and the pressure supply valve PSV, are opened on conditions while all the valves for the stoves in the state of on gas are closed, cooled air from the cold blast main pipe 11 being supplied to the regeneration chamber 12 of the hot blast stove lHS.

When the difference between the pressure within cold blast main pipe 11 and that within the regeneration chamber 12 of the hot blast stove lHS reaches a predetermined value, the primary pressure supply valve PSV and the pressure supply valve PSV, are closed, the blast valve CV being opened, the hot blast valve HV being opened, whereby hot air is supplied to the hot blast main pipe 15.

The temperature within the hot blast main pipe 15 is controlled by an independent controlling device (not shown).

The foregoing is the description in connection with the first hot blast stove lHS, and the same is applicable to each of the other hot blast stoves 2H8 41-15.

As described hereinbefore, each of the hot blast stoves lHS 4l-IS is operated intermittently, and more than one such stove are operated in the order as illustrated in FIG. 2.

The hot blast stoves lHS 4l-IS are set in the state as indicated hereinunder.

4H5 on blast 3H8 on blast 2HS on gas lHS on gas FIG. 2 shows the state of switchover when a blast signal is given to the hot blast stove 3H8 when the state of operation of each hot blast stove is as described above.

First, a signal (a) is given to the hot blast stove lHS and 3HS thereby causing alarm bells STX STX to ring. Then the primary gas valve GV of the hot blast stove IHS starts to close, the blast valve CV;; of the hot blast stove 3HS starts to close, the cold blast valve CV and the hot blast valve HV being completely closed.

The hot blast stove 3HS waits for a next instruction in the state as described hereinbefore.

In the hot blast stove lHS, the primary gas valve GV is completely closed, the gas shut-off valve BV is then closed, the air shut-off valve AV is then closed, and the stack valves SVA SVB are then closed, whereby the process from on gas to repose is completed. Then in the hot blast stove lHS the process is switched over from repose to on blast, the hot blast stove 3HS switches the process from repose to on gas, the alarm bell STX,, STX ringing, the pressure supply valves PSV and PSV being opened, whereby the blast pressure within the hot blast stove 3HS is supplied to the cold blast branch pipe 18 through pressure supply valve PSV The blast pressure supplied to the branch pipe 18 enters the hot blast stove lHS through the pressure supply valve PSV The pressure supply valves PSV and PSV are maintained in an open state until the time limit predetermined by a timer TM the blast pressure within the hot blast stove 3HS being supplied to the hot blast stove lI-IS during the lapse of time predetermined by said timer TM The supply of pressure is supervised by the blast pressure (not shown) of each stove, approximately one half of the pressure being transferred to the hot blast stove lHS. Therefore, the time limit predetermined by the timer 'I'M is computed by an electronic data processing system so as to make it possible to supply one half of the pressure as described hereinbefore.

Thus, after the lapse of time predetermined by the timer TM,, the pressure supply valve PSV is closed, and the primary pressure supply valve PSV is opened, whereby insufficient blast pressure is supplied to the hot blast stove lHS from the blast main pipe 11 through the primary pressure supply valve PSV the cooling air branch pipe 18 and the pressure supply valve PSV This pressure supply is effected exclusively within the time limit predetermined by the timer TM The hot blast stove 3HS, with the completion of the first-stage work, is transferred to the state of on gas. The remaining blast pressure is discharged into the flue 14 through the stack valve SVA This discharge is effected exclusively within the time limit predetermined by the timer T8 a succeeding process starting thereafter.

The supply and discharge of pressure are effected by making use of the timers TM TM T8 T3 TB provided on the hot blast stoves lI-IS and 3H8, respectively. However, the operation is carried on similarly also in case of other methods, for example, a combination of a pressure difference detector a, pressure measuring device and an electronic computing system. In the first hot blast stove lHS during the process leading up to on blast,; the pressure supply valves PSV and PSV, after the lapse of the time limit predetermined by the timer TS are closed, the cold blast valve CV being completely opened synchronously with the cleaning signal, and then the hot blast valve I-IV being is opened, whereby the first hot blast stove is placed in a state parallel with the hot blast stove 4HS already in the state of on blast.

In the hot blast stove 3H8, the stack valves SVA and SVB are completely opened simultaneously with the termination of the blasting, and the air shut-off valve Av,,, gas shut-off valve BV;,, and gas valve GV are opened, whereby transfer to the on gas state is completed and regeneration is commenced. For the foregoing processes, the stoves respectively are selected automatically by a program set by a relay or an electronic data processing system, the opening and closing of each valve also being adapted to be automatically conducted in a predetermined order.

Now the switchover of the stoves and the variation of pressure will be explained hereinunder in reference to FIG. 3.

FIG. 3 shows the state of operation of the same stove as illustrated in FIG. 2, i.e., the hot blast stoves 3H5 and 4HS are in the state of on blast, the hot stoves lHS and 2HS being in the state ofon gas in FIG. 3 I, the parallel line on the upper side of each horizontal line 10 showing each stove indicates the state of on blast, the parallel line on the lower side indicating the state of on gas, the oblique line indicating transfer to either on gas or on blast respectively. In FIG. 3 ll showing pressure within the stove, the oblique line indicates either a rise or a fall of pressure, the parallel lines indiating the state in which on blast is being supplied with an accumulation of predetermined pressure.

In FIG. 3, the hot blast stove lI-IS is transferred from the state of on gas to repose by the signal(a). When the hot'blast stove 3H5 is in the state of repose, the hot blast stove lHS starts into the on blast state, the pressure within the hot blast stove lI-IS commencing to rise from the point A simultaneously with the pressure within the hot blast stove 3HS commencing to fall until it becomes substantially same as that of the hot blast stove lHS, as indicated at the point B.

When the process has proceeded to the point B, the hot blast stove commences a preliminary action for the next process, the pressure within the stove becoming same as the atmosphere.

In the hot blast stove IHS, transfer to the on blast process is continued, said transfer and transfer to the combustion process in the hot blast stove 3HS being completed at the point C.

Subsequently, the state of on blast continues in the hot blast stove lI-IS, the state of combustion being continued in the hot blast stove 3H5. For signals (b), (c), (d), the same process is conducted though the order of the hot blast stoves varies. The embodiment comprises four units of hot blast stoves, but the switchover process is same for more than four units of hot blast stoves excepting for an increase in the number of signals.

As described hereinbefore, the hot blast stove of this invention is characterized in that pressure is supplied to the stove on the occasion of transfer to the on blast from the on gas process after a repose, the pressure within the hot blast pipe being free from any effect even during the supply of pressure. Since the pressure is supplied by making use of the residual pressure of the on blast state from another hot blast stove, the heat efficiency is better in the present invention than in case of the conventional method in which cool air is blown into the stove. And, when transfer to the on gas is effected after completion of blast, the blast pressure of the stove is reduced by half to resulting in the shortening of discharge time thereby making it possible to protect the smoke duct. Moreover, the present invention makes it possible to dispense with the use of a program setting device, timer, electronic data processing system and the like at the time of commencing blast for the blast stove required in case of the conventional method thereby making it possible to stabilize the operation due to the flexibility of this invention a, which makes it adaptable to whatever system that may require a change.

What is claimed is:

1. A method of operating a system of hot blast stoves for a blast furnace which system is made up of a plurality of hot blast stoves each having a cold blast valve, a pressure supply valve, a flue valve and a hot blast valve, the system further having a cold blast main pipe to which the cold blast valves of all of the stoves are connected, a cold blast branch pipe branching from said cold blast main pipe with a branch pipe pressure supply valve therebetween and to which all of the pressure supply valves are connected, a stack to which all of the flue valves are connected, and a hot blast pipe to which all of the hot blast valves are connected, said method comprising supplying combustion fuel to at least one of the stoves for heating it in an on blast operation while keeping the cold blast valve, pressure supply valve and hot blast valve to the one stove closed and leaving the flue valve open, while at the same time operating at least one other stove in an on regneration operation by keeping the cold blast valve and the hot blast valve open and the flue valve and the pressure supply valve closed, thereby to pass cold gas through the said other stove to heat it, and then switching over the operation of the one stove to an on regeneration operation and the other stove to and on blast operation by first closing the cold blast valve and the hot blast valve of said other stove, and opening the pressure supply valve thereof while closing the branch pipe pressure supply valve, and at the same time closing the flue valve and ending the fuel supply to the other stove and opening only the pressure supply valve thereof for admitting the hot gas from the other stove to the one stove through the cold blast branch pipe, and thereafter closing the pressure supply valve of the said other stove and opening the flue valve thereof and starting supply of fuel thereto, while closing the pressure supply valve of the one stove opening the cold blast valve and the hot blast valve thereof. 

1. A method of operating a system of hOt blast stoves for a blast furnace which system is made up of a plurality of hot blast stoves each having a cold blast valve, a pressure supply valve, a flue valve and a hot blast valve, the system further having a cold blast main pipe to which the cold blast valves of all of the stoves are connected, a cold blast branch pipe branching from said cold blast main pipe with a branch pipe pressure supply valve therebetween and to which all of the pressure supply valves are connected, a stack to which all of the flue valves are connected, and a hot blast pipe to which all of the hot blast valves are connected, said method comprising supplying combustion fuel to at least one of the stoves for heating it in an on blast operation while keeping the cold blast valve, pressure supply valve and hot blast valve to the one stove closed and leaving the flue valve open, while at the same time operating at least one other stove in an on regneration operation by keeping the cold blast valve and the hot blast valve open and the flue valve and the pressure supply valve closed, thereby to pass cold gas through the said other stove to heat it, and then switching over the operation of the one stove to an on regeneration operation and the other stove to and on blast operation by first closing the cold blast valve and the hot blast valve of said other stove, and opening the pressure supply valve thereof while closing the branch pipe pressure supply valve, and at the same time closing the flue valve and ending the fuel supply to the other stove and opening only the pressure supply valve thereof for admitting the hot gas from the other stove to the one stove through the cold blast branch pipe, and thereafter closing the pressure supply valve of the said other stove and opening the flue valve thereof and starting supply of fuel thereto, while closing the pressure supply valve of the one stove opening the cold blast valve and the hot blast valve thereof. 